Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			$ 5,097
Other comprehensive income (loss)	$ (80)	$ 65	(168)	$ 27
AOCI, ending balance	(2,921)		(2,921)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			(2,727)	(2,586)
Other comprehensive income (loss) before reclassifications			(66)	60
Net losses reclassified from accumulated other comprehensive loss			234	(87)
Other comprehensive income (loss)			(168)	27
AOCI, ending balance	(2,559)	(2,613)	(2,559)	(2,613)
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			(439)	(1,435)
Other comprehensive income (loss) before reclassifications			(250)	602
Net losses reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income (loss)			250	(602)
AOCI, ending balance	(689)	(833)	(689)	(833)
Net investment hedging activities
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			(203)	140
Other comprehensive income (loss) before reclassifications			73	(307)
Net losses reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income (loss)			(73)	307
AOCI, ending balance	(130)	(167)	(130)	(167)
Pension and post- employment benefits
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			(1,919)	(1,513)
Other comprehensive income (loss) before reclassifications			7	(37)
Net losses reclassified from accumulated other comprehensive loss			92	58
Other comprehensive income (loss)			(99)	(21)
AOCI, ending balance	(1,820)	(1,492)	(1,820)	(1,492)
Marketable security activities
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			0	46
Other comprehensive income (loss) before reclassifications			(6)	31
Net losses reclassified from accumulated other comprehensive loss			4	(49)
Other comprehensive income (loss)			2	18
AOCI, ending balance	(2)	28	(2)	28
Cash flow hedging activities
AOCI Attributable to Parent, Net of Tax
AOCI, beginning balance			(166)	176
Other comprehensive income (loss) before reclassifications			110	(229)
Net losses reclassified from accumulated other comprehensive loss			138	(96)
Other comprehensive income (loss)			(248)	325
AOCI, ending balance	$ 82	$ (149)	$ 82	$ (149)